The present invention relates to a dielectric ceramic composition and a ceramic capacitor fabricated using the same, and more particularly, to a dielectric ceramic composition having excellent temperature characteristics and a long life-time and to a ceramic capacitor comprising a dielectric layer formed from said composition.
A ceramic capacitor generally consists of a sintered body in the form of a chip, and a pair of external electrodes formed on both terminals of the chip. The sintered body is a multi-layered material wherein several dielectric layers and internal electrodes are alternately laminated. In such a multilayer capacitor, adjacent two internal electrodes are aligned with one dielectric layer sandwitched therebetween and are each electrically connected to the external electrodes.
As a material for forming a dielectric layer of a ceramic capacitor, there has been hitherto employed, e.g., a reduction resistive dielectric ceramic composition comprising barium titanate (BaTiO3) as a major component, and a rare earth metal element as an additional component. Further, as a material for forming an internal electrode of a ceramic capacitor, a sintered conductive paste comprising, e.g., a Ni metal powder as a major component has been employed.
The sintered body of a ceramic capacitor may be prepared by overlaying a green ceramic sheet and an internal electrode pattern alternately and intimately to provide a multi-layered chip, evaporating a binder component from the chip, sintering the chip at a high temperature of about 1200xcx9c1300xc2x0 C. under a non-oxidizing atmosphere and then subjecting the sintered chip to a re-oxidization under a weakly oxidizing atmosphere.
Recently, there exists a need to develop electronic parts as well as electronic machines having enhanced electrical properties. Particularly, in case of a ceramic capacitor, many efforts have been made to improve the temperature and life-time characteristics.
It is, therefore, a primary object of the invention to provide a dielectric ceramic composition having improved temperature characteristics and a long life-time.
It is a second object of the invention to provide a ceramic capacitor comprising a dielectric layer formed from the inventive dielectric ceramic composition.
In accordance with an aspect of the present invention, there is provided a dielectric ceramic composition comprising a sintered body containing ceramic particles having a core/shell structure (hereinafter, xe2x80x9ccore/shell structured particlesxe2x80x9d) in an amount of 15% or more based on the total ceramic particles of the sintered body, the core/shell structured particle being composed of a core portion, which is a BaTiO3 crystal, and a shell portion surrounding the core, which is made of a solid solution containing BaTiO3 as a major component.
Further, in accordance with the present invention, there is provided a ceramic capacitor comprising at least one dielectric ceramic layer formed from the inventive dielectric ceramic composition, and at least two internal electrodes between which the dielectric ceramic layer is inserted.